<PAGE>

                                                                   Exhibit 10.31

GNU GENERAL PUBLIC LICENSE

VERSION 2, JUNE 1991
Copyright (C) 1989, 1991 Free Software Foundation, Inc.

675 Mass Ave, Cambridge, MA 02139, USA Everyone is permitted to copy and
distribute verbatim copies of this license document, but changing it is not
allowed.

PREAMBLE

The licenses for most software are designed to take away your freedom to share
and change it. By contrast, the GNU General Public License is intended to
guarantee your freedom to share and change free software -- to make sure the
software is free for all its users. This General Public License applies to most
of the Free Software Foundation's software and to any other program whose
authors commit to using it. (Some other Free Software Foundation software is
covered by the GNU Library General Public License instead.) You can apply it to
your programs, too.

When we speak of free software, we are referring to freedom, not price. Our
General Public Licenses are designed to make sure that you have the freedom to
distribute copies of free software (and charge for this service if you wish),
that you receive source code or can get it if you want it, that you can change
the software or use pieces of it in new free programs; and that you know you can
do these things.

To protect your rights, we need to make restrictions that forbid anyone to deny
you these rights or to ask you to surrender the rights. These restrictions
translate to certain responsibilities for you if you distribute copies of the
software, or if you modify it.

For example, if you distribute copies of such a program, whether gratis or for a
fee, you must give the recipients all the rights that you have. You must make
sure that they, too, receive or can get the source code. And you must show them
these terms so they know their rights.

We protect your rights with two steps: (1) copyright the software, and

(2) offer you this license which gives you legal permission to copy, distribute
and/or modify the software.

     Also, for each author's protection and ours, we want to make certain that
everyone understands that there is no warranty for this free software. If the
software is modified by someone else and passed on, we want its recipients to
know that what they have is not the original, so that any problems introduced by
others will not reflect on the original authors' reputations.

Finally, any free program is threatened constantly by software patents. We wish
to avoid the danger that redistributors of a free program will individually
obtain patent licenses, in effect making the program proprietary. To prevent
this, we have made it clear that any patent must be licensed for everyone's free
use or not licensed at all.

<PAGE>

The precise terms and conditions for copying, distribution and modification
follow.

GNU GENERAL PUBLIC LICENSE

TERMS AND CONDITIONS FOR COPYING, DISTRIBUTION AND MODIFICATION

0. This License applies to any program or other work which contains a notice
placed by the copyright holder saying it may be distributed under the terms of
this General Public License. The "Program", below, refers to any such program or
work, and a "work based on the Program" means either the Program or any
derivative work under copyright law: that is to say, a work containing the
Program or a portion of it, either verbatim or with modifications and/or
translated into another language. (Hereinafter, translation is included without
limitation in the term "modification".) Each licensee is addressed as "you".

Activities other than copying, distribution and modification are not covered by
this License; they are outside its scope. The act of running the Program is not
restricted, and the output from the Program is covered only if its contents
constitute a work based on the Program (independent of having been made by
running the Program). Whether that is true depends on what the Program does.

     1.  You may copy and distribute verbatim copies of the Program's source
         code as you receive it, in any medium, provided that you conspicuously
         and appropriately publish on each copy an appropriate copyright notice
         and disclaimer of warranty; keep intact all the notices that refer to
         this License and to the absence of any warranty; and give any other
         recipients of the Program a copy of this License along with the
         Program.

         You may charge a fee for the physical act of transferring a copy, and
         you may at your option offer warranty protection in exchange for a fee.

     2.  You may modify your copy or copies of the Program or any portion of it,
         thus forming a work based on the Program, and copy and distribute such
         modifications or work under the terms of Section 1 above, provided that
         you also meet all of these conditions:

         a)   You must cause the modified files to carry prominent notices
              stating that you changed the files and the date of any change.

         b)   You must cause any work that you distribute or publish, that in
              whole or in part contains or is derived from the Program or any
              part thereof, to be licensed as a whole at no charge to all third
              parties under the terms of this License.

         c)   If the modified program normally reads commands interactively when
              run, you must cause it, when started running for such interactive
              use in the most ordinary way, to print or display an announcement
              including an appropriate copyright notice and a notice that there
              is no warranty (or else, saying that you provide a warranty) and
              that users may redistribute the program under these conditions,
              and telling the user how to view a copy of this License.
              (Exception: if the Program itself is interactive but does not
              normally print

<PAGE>

              such an announcement, your work based on the Program is not
              required to print an announcement.)

These requirements apply to the modified work as a whole. If identifiable
sections of that work are not derived from the Program, and can be reasonably
considered independent and separate works in themselves, then this License, and
its terms, do not apply to those sections when you distribute them as separate
works. But when you distribute the same sections as part of a whole which is a
work based on the Program, the distribution of the whole must be on the terms of
this License, whose permissions for other licensees extend to the entire whole,
and thus to each and every part regardless of who wrote it.

Thus, it is not the intent of this section to claim rights or contest your
rights to work written entirely by you; rather, the intent is to exercise the
right to control the distribution of derivative or collective works based on the
Program.

In addition, mere aggregation of another work not based on the Program with the
Program (or with a work based on the Program) on a volume of a storage or
distribution medium does not bring the other work under the scope of this
License.

     3.  You may copy and distribute the Program (or a work based on it, under
         Section 2) in object code or executable form under the terms of
         Sections 1 and 2 above provided that you also do one of the following:

              a)  Accompany it with the complete corresponding machine-readable
                  source code, which must be distributed under the terms of
                  Sections 1 and 2 above on a medium customarily used for
                  software interchange; or,

              b)  Accompany it with a written offer, valid for at least three
                  years, to give any third party, for a charge no more than your
                  cost of physically performing source distribution, a complete
                  machine-readable copy of the corresponding source code, to be
                  distributed under the terms of Sections 1 and 2 above on a
                  medium customarily used for software interchange; or,

              c)  Accompany it with the information you received as to the offer
                  to distribute corresponding source code. (This alternative is
                  allowed only for noncommercial distribution and only if you
                  received the program in object code or executable form with
                  such an offer, in accord with Subsection b above.)

The source code for a work means the preferred form of the work for making
modifications to it. For an executable work, complete source code means all the
source code for all modules it contains, plus any associated interface
definition files, plus the scripts used to control compilation and installation
of the executable. However, as a special exception, the source code distributed
need not include anything that is normally distributed (in either source or
binary form) with the major components (compiler, kernel, and so on) of the
operating system on which the executable runs, unless that component itself
accompanies the executable.

If distribution of executable or object code is made by offering access to copy
from a designated place, then offering equivalent access to copy the source code
from the same

<PAGE>

place counts as distribution of the source code, even though third parties are
not compelled to copy the source along with the object code.

     4.  You may not copy, modify, sublicense, or distribute the Program except
         as expressly provided under this License. Any attempt otherwise to
         copy, modify, sublicense or distribute the Program is void, and will
         automatically terminate your rights under this License. However,
         parties who have received copies, or rights, from you under this
         License will not have their licenses terminated so long as such parties
         remain in full compliance.

     5.  You are not required to accept this License, since you have not signed
         it. However, nothing else grants you permission to modify or distribute
         the Program or its derivative works. These actions are prohibited by
         law if you do not accept this License. Therefore, by modifying or
         distributing the Program (or any work based on the Program), you
         indicate your acceptance of this License to do so, and all its terms
         and conditions for copying, distributing or modifying the Program or
         works based on it.

     6.  Each time you redistribute the Program (or any work based on the
Program), the recipient automatically receives a license from the original
licensor to copy, distribute or modify the Program subject to these terms and
conditions. You may not impose any further restrictions on the recipients'
exercise of the rights granted herein. You are not responsible for enforcing
compliance by third parties to this License.

     7.  If, as a consequence of a court judgment or allegation of patent
         infringement or for any other reason (not limited to patent issues),
         conditions are imposed on you (whether by court order, agreement or
         otherwise) that contradict the conditions of this License, they do not
         excuse you from the conditions of this License. If you cannot
         distribute so as to satisfy simultaneously your obligations under this
         License and any other pertinent obligations, then as a consequence you
         may not distribute the Program at all. For example, if a patent license
         would not permit royalty-free redistribution of the Program by all
         those who receive copies directly or indirectly through you, then the
         only way you could satisfy both it and this License would be to refrain
         entirely from distribution of the Program.

         If any portion of this section is held invalid or unenforceable under
         any particular circumstance, the balance of the section is intended to
         apply and the section as a whole is intended to apply in other
         circumstances.

         It is not the purpose of this section to induce you to infringe any
         patents or other property right claims or to contest validity of any
         such claims; this section has the sole purpose of protecting the
         integrity of the free software distribution system, which is
         implemented by public license practices. Many people have made generous
         contributions to the wide range of software distributed through that
         system in reliance on consistent application of that system; it is up
         to the author/donor to decide if he or she is willing to distribute
         software through any other system and a licensee cannot impose that
         choice.

         This section is intended to make thoroughly clear what is believed to
         be a consequence of the rest of this License.

<PAGE>

     8.  If the distribution and/or use of the Program is restricted in certain
         countries either by patents or by copyrighted interfaces, the original
         copyright holder who places the Program under this License may add an
         explicit geographical distribution limitation excluding those
         countries, so that distribution is permitted only in or among countries
         not thus excluded. In such case, this License incorporates the
         limitation as if written in the body of this License.

     9.  The Free Software Foundation may publish revised and/or new versions of
         the General Public License from time to time. Such new versions will be
         similar in spirit to the present version, but may differ in detail to
         address new problems or concerns.
         Each version is given a distinguishing version number. If the Program
         specifies a version number of this License which applies to it and "any
         later version", you have the option of following the terms and
         conditions either of that version or of any later version published by
         the Free Software Foundation. If the Program does not specify a version
         number of this License, you may choose any version ever published by
         the Free Software Foundation.

     10. If you wish to incorporate parts of the Program into other free
         programs whose distribution conditions are different, write to the
         author to ask for permission. For software which is copyrighted by the
         Free Software Foundation, write to the Free Software Foundation; we
         sometimes make exceptions for this. Our decision will be guided by the
         two goals of preserving the free status of all derivatives of our free
         software and of promoting the sharing and reuse of software generally.

NO WARRANTY

     11. BECAUSE THE PROGRAM IS LICENSED FREE OF CHARGE, THERE IS NO WARRANTY
         FOR THE PROGRAM, TO THE EXTENT PERMITTED BY APPLICABLE LAW. EXCEPT WHEN
         OTHERWISE STATED IN WRITING THE COPYRIGHT HOLDERS AND/OR OTHER PARTIES
         PROVIDE THE PROGRAM "AS IS" WITHOUT WARRANTY OF ANY KIND, EITHER
         EXPRESSED OR IMPLIED, INCLUDING, BUT NOT LIMITED TO, THE IMPLIED
         WARRANTIES OF MERCHANTABILITY AND FITNESS FOR A PARTICULAR PURPOSE. THE
         ENTIRE RISK AS TO THE QUALITY AND PERFORMANCE OF THE PROGRAM IS WITH
         YOU. SHOULD THE PROGRAM PROVE DEFECTIVE, YOU ASSUME THE COST OF ALL
         NECESSARY SERVICING, REPAIR OR CORRECTION.

     12. IN NO EVENT UNLESS REQUIRED BY APPLICABLE LAW OR AGREED TO IN WRITING
         WILL ANY COPYRIGHT HOLDER, OR ANY OTHER PARTY WHO MAY MODIFY AND/OR
         REDISTRIBUTE THE PROGRAM AS PERMITTED ABOVE, BE LIABLE TO YOU FOR
         DAMAGES, INCLUDING ANY GENERAL, SPECIAL, INCIDENTAL OR CONSEQUENTIAL
         DAMAGES ARISING OUT OF THE USE OR INABILITY TO USE THE PROGRAM
         (INCLUDING BUT NOT LIMITED TO LOSS OF DATA OR DATA BEING RENDERED
         INACCURATE OR LOSSES

<PAGE>

         SUSTAINED BY YOU OR THIRD PARTIES OR A FAILURE OF THE PROGRAM TO
         OPERATE WITH ANY OTHER PROGRAMS), EVEN IF SUCH HOLDER OR OTHER PARTY
         HAS BEEN ADVISED OF THE POSSIBILITY OF SUCH DAMAGES.

END OF TERMS AND CONDITIONS

APPENDIX: HOW TO APPLY THESE TERMS TO YOUR NEW PROGRAMS

If you develop a new program, and you want it to be of the greatest possible use
to the public, the best way to achieve this is to make it free software which
everyone can redistribute and change under these terms.

To do so, attach the following notices to the program. It is safest to attach
them to the start of each source file to most effectively convey the exclusion
of warranty; and each file should have at least the "copyright" line and a
pointer to where the full notice is found.

<one line to give the program's name and a brief idea of what it does.>

     Copyright (C) 19yy  <name of author>

This program is free software; you can redistribute it and/or modify it under
the terms of the GNU General Public License as published by the Free Software
Foundation; either version 2 of the License, or (at your option) any later
version.

     This program is distributed in the hope that it will be useful, but WITHOUT
     ANY WARRANTY; without even the implied warranty of MERCHANTABILITY or
     FITNESS FOR A PARTICULAR PURPOSE. See the GNU General Public License for
     more details.

     You should have received a copy of the GNU General Public License along
     with this program; if not, write to the Free Software Foundation, Inc., 675
     Mass Ave, Cambridge, MA 02139, USA.

Also add information on how to contact you by electronic and paper mail.

If the program is interactive, make it output a short notice like this when it
starts in an interactive mode:

     Gnomovision version 69, Copyright (C) 19yy name of author

Gnomovision comes with ABSOLUTELY NO WARRANTY; for details type `show w'.This is
free software, and you are welcome to redistribute it under certain conditions;
type `show c' for details.

The hypothetical commands `show w' and `show c' should show the appropriate
parts of the General Public License. Of course, the commands you use may be
called something other than `show w' and `show c'; they could even be
mouse-clicks or menu items -- whatever suits your program.

You should also get your employer (if you work as a programmer) or your school,
if any, to sign a "copyright disclaimer" for the program, if necessary. Here is
a sample; alter the names:

<PAGE>

  Yoyodyne, Inc., hereby disclaims all copyright interest in the program
  'Gnomovision' (which makes passes at compilers) written by James Hacker.

  <signature of Ty Coon>, 1 April 1989
  Ty Coon, President of Vice

This General Public License does not permit incorporating your program into
proprietary programs. If your program is a subroutine library, you may consider
it more useful to permit linking proprietary applications with the library. If
this is what you want to do, use the GNU Library General Public License instead
of this License.